High voltage cable termination



Nov. 24, 1970 A. JOHNSON ET AL 3,542,942

HIGH VOLTAGE CABLE TERMINATION Filed Sept. 25, 1969 A a/WWO OHIVJO/l BYfig/P040 CHaeV/q' j I W i ATTQP/VZ-YJ United States Patent Office3,542,942 Patented Nov. 24, 1970 US. Cl. 174-73 7 Claims ABSTRACT OF THEDISCLOSURE An effective outdoor terminal of simple and economicalstructure for high 'voltage electrical cables, consisting of an elongateporcelain tube with close-fitting conical semiconductive rubbery endcaps encircled by conductive flashover bands, the whole being providedwith a filling of an insulating grease.

This invention relates to terminators for high voltage electrical cablehaving a conductive sheath. The terminator combines a highly insulativeand track-resistant elongate ceramic tube forming the body of the devicewith semiconductive elastic end caps for axially supporting the tube onthe conductor. The device therefore combines high insulative qualitieswith ease of assembly and application, and with economy of construction.

In the drawing,

FIG. 1 is a view in elevation and largely in cross section of apreferred form of terminator as applied to a high voltage cable end,

FIG. 2 is a section taken at line 2-2 of FIG. 1,

FIG. 3 is a vertical section of the lower end cap of the device of FIG.1 prior to installation, and

FIG. 4 is a section taken approximately at line 44 of FIG. 1 of aportion of a structure similar to that of FIG. 1 but including analternative form of encircling band and support.

The terminator of FIG. 1 includes an insulative externally annularlycorrugated and grooved elongate porcelain ceramic tube 11 serving as thebody of the device. semiconductive rubbery cap 12 fits over the upperend of the body 11 and around the constricted neck portion 13, beingheld in place both by its natural resiliency and by an encircling metalretaining band 14, the latter serving also as a flashover band toprevent localized concentration within the semiconductive cap of anyexcessive voltages. The neck 13 is externally grooved to form a narrowannular groove 15, and the cap 12 is preferably correspondinglyannularly internally ridged, the ridge 16 fitting within the groove 15.A similar groove and ridge construction is illustrated 'at the small endof the cap 12. Nordel conductive ethylene-propylene terpolymer is aneffective material of construction for such caps.

The lower end of the body 11 similarly terminates in a doubly annularlygrooved neck 17 over which is applied a conical semiconductive elasticcap 18 of Nordel conductive polymer held in place by a retaining ring19. The inner surface 20 of the thickened lower portion of the cone 18has a stress cone configuration and is grounded to the conductive sheath21 of the cable 22 and preferably also through the ring 19 to anexternal ground 23 as shown.

The interior of the structure is preferably partially filled with athixotropic insulating grease, in a quantity sufiicient substantially tofill all voids remaining after insertion of a cable end. Although suchgreases do not ordinarily flow under normal ambient and handlingconditions, it is usually desirable to seal the ends of the terminatorstructure prior to installation, to prevent both loss of grease andentry of dirt or other contamination. Ordinarily removable plub sealsmay be used, but the incorporation within the cap members of puncturablediaphragm retaining elements offers a number of advantages and ispreferred. The diaphragms retain the grease under all ordinaryconditions during storage and handling prior to installation, but areeasily punctured and displaced by insertion of the conductor elements. Aresidual portion of such a diaphragm is shown in FIGS. 1 and 2 asfragment 24.

The typical installation of FIG. 1 shows the cable 22 from which aterminal portion of insulation 33 has been removed to expose theconductor 25. Permanent contact with a terminally pierced connectorelement 26 is made through an intermediate compression or crimpingsleeve 27, and the assembly is then pushed into and through theterminator 10 as shown. The end cap 18 fits tightly about and providesconductive contact with the sheath 21, and the cap 12 similarly fitstightly about the element 26. The grease contained within the assemblyserves to fill most of the voids otherwise present and to assure waterresistant connections at both ends. The conductor 25 and element 26 arefirmly held at the axis of the tube 11 and of the entire structure.

FIG. 3 shows the structure of the lower cap 18 prior to assembly on thetube 11 and cable 21, and in particular illustrates the location ofdiaphragm 28. This item is inset slightly from the smaller extremity ofthe cap for convenience in inserting the conductor 26, but sufficientlyaway from the surface 20 of the stress cone area to avoid undesirableelectrical effects at that area.

Where the band 19 is shown as a continuous band in FIGS. 1 and 2, andmust therefore be driven over the cap 12, the band 19' encircling thecap 18 is illustrated in FIG. 4 to be in the form of an adjustable clampmember having outturned ends 29 secured together by means of a bolt 30.Additionally, the ring 19' is supported on a bracket member 31 which maybe attached to a pole or other supporting structure, e.g., by screw 32.

What is claimed is as follows:

1. A high voltage cable terminator assembly comprising an insulativeexteriorly annularly corrugated and glazed elongate ceramic tube havingat each end a generally conical semiconductive rubbery cap having alarger end, encircling the end of said tube and being in turn encircledwith a metal retaining band, and an open smaller end for fitting closelyabout a high voltage line component.

2. The assembly of claim 1 containing a quantity of thixotropicinsulative grease.

3. The assembly of claim 2 including a grease-retaining diaphragm withineach of said end caps.

4. The assembly of claim 1 wherein the one of said end caps which is tobe placed over the cable-end has a stress cone configuration.

5. The assembly of claim 4 wherein the metal band encircling the caphaving the stress cone configuration terminator.

' 6. The assembly of claim 4 in position on a terminal of a high voltagecable enclosed within a conductive 5 sheath, wherein the cap having thestress cone configuration is disposed over the cable sheath and the bandencircling said cap is grounded.

7. The assembly of claim 6 wherein said band serves as a component of asupporting bracket.

References Cited UNITED STATES PATENTS 3,322,883 5/1967 Lusk 174-733,377,420 4/1968 Brown et al. 174-73 LARAMIE E. ASKIN, Primary ExaminerUS. 01. X.R.

